Planing Hull with Concentric Pad Keel

ABSTRACT

By including a Concentric Pad Keel, a watercraft experiences a reduction in Slamming forces as well as generally improved Seakeeping and Seakindliness.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/994,823 filed May 16, 2014, the disclosures of which are herein incorporated by reference.

TECHNICAL FIELD

The field discussed herein relates generally to watercraft hull configuration.

BACKGROUND

It is well known that fiat, zero-deadrise hull surfaces have the highest planing efficiencies, and many prior art watercraft incorporate flat sections to bull bottoms to improve total hull planing efficiency. Planing efficiency refers to efficiency of energy use while underway; a hull having high planing efficiency can use less fuel and produce less wake than a hull having low planing efficiency. However, it is also well known that wide, flat planing surfaces generate strong impacts to the hull (and watercraft occupants) when such a planing surface re-contacts the water surface after separating from the water surface, for instance when planing through choppy conditions and when re-contacting the water surface after the watercraft launches off wave crests. These strong impacts are called “watercraft slamming”. To minimize slamming associated with flat planing hulls, prior art watercraft have limited the flat hull areas to selective portions of the hull. Typically, the flat hull areas employed by prior art watercraft have been relatively short, narrow, wedge or delta-shaped areas of the hull keel that are widest at the transom, taper in width forward from the transom, and blend into V-shaped sections in the hull's forebody.

Some prior art watercraft designs employ truncated, or “padded”. V-shaped hull structures wherein the bottom of a V-shaped hull has been cut away (“truncated”) to create a flat “pad” area integral to the hull's bottom. Other prior art watercraft have employed distinctly “flat pad keels” wherein the flat pad projects below the theoretical convergence of the sides of a watercraft's V-shaped hull. it is well known that truncated V-shaped hulls and pad keels can cause maneuvering and turning problems such as side slip and lack of directionality. As a result, prior art watercraft with flat hull portions frequently added snakes, reverse snakes, sponsons or other structures to the hull to increase hull grip.

FIG. 0A shows a relationship between lift fraction of flat plate and deadrise, but does not explain the relationship of slamming force to those variables. As shown by FIG. 0A, the 0 deadrise of a pad keel provides significantly more lift, about 33% more than a 20 degree deadrise V-shaped hull. There is unmet demand for a hull design with >45 Deadrise Pad Keel Sides with improved Seakindliness, Seakeeping, substantially reduced Slamming, with less viscous drag and minimal reduction in Planing Efficiency and with Acceptable Slamming Force. Therefore, the technical problem to be solved is to design a Hull that combines a large Pad Keel with Pad Keel Sides whose deadrise angles of 45 degrees or greater create a Hull with improved Seakindliness, Seakeeping, substantially reduced Slamming, with minimal reduction in Planing Efficiency, compared to prior art deep V-hulls and Planing Hulls.

The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent upon a reading of the specification and a study of the drawings.

SUMMARY

The following examples and aspects thereof are described and illustrated in conjunction with systems, tools, and methods that are meant to be exemplary and illustrative, not limiting in scope. In various examples, one or more of the above-described problems have been reduced or eliminated, while other examples are directed to other improvements.

As discussed herein, watercraft can benefit from Hull designs utilizing Concentric Pad Keels of varying width, surface shape, and Taper. Such Hull designs can include a Self Flooding and Self-Bailing Pad Keel Plenum equipped with a Bow Pocket Vent.

As shown by FIG. 0A, the 0 deadrise of a pad keel provides significantly more lift, about 33% more than a 20 degree deadrise V-shaped hull. Therefore, this allows the Pad Keel Sides to be designed to mitigate slamming rather than generating lift, FIG. 0B shows the effects of deadrise and the relationship between pressure forces of wedge sections (e.g. a V-shaped hull) from initial entry through increasing immersion. If the Pad Keel Sides have deadrise angles of 45 degrees or greater, the peak slamming, pressure as the hull is immersed will be no greater than the initial entry pressure.

Advantageously, Hull designs benefiting from these advancements outperform those having, merely flat surfaces, V-shaped, previous Pad Keel hulls. Hull designs including advancements disclosed herein enjoy high Planing efficiency without high Slamming, and exhibit excellent Seakindliness and Seakeeping. By analogy, the hydrodynamic properties of a Concentric Pad Keel allow it to function on a watercraft like an automotive strut or shock absorber functions on a car. This improves the experience of operating the watercraft in the way that an automotive shock absorber improves the experience of driving a car.

Herein is described a Hull configuration employing Concentric Pad Keels of varying width, surface shape, Taper, and Deadrise depending on the purpose of the craft). Embodiments of the Hull can include a Pad Keel Plenum that Self-Floods and Self-Bails via a Bow Pocket Vent on the Pad Keel Sides. Advantageously, this provides a novel watercraft made with the Hull that has improved Seakeeping, Seakindliness, payload, and Planing efficiency, and reduced Slamming compared with prior art Planing hulls and V-Hulls. This is achieved by combining the efficiency benefits of a wider and/or multiple Pad Keels without having negative Seakeeping or handling problems associated with a Deep-V The Hull of the invention can be retrofitted to existing watercraft and can be employed in new watercraft designs.

The Self-Flooding and Self-Bailing Pad Keel embodiments of the invention dynamically improve Seakeeping and Seakindliness over a range of speeds. A Bow Pocket Vent provides atmospheric air ingress to the interior of a Hollow Plenum and allows the Plenum to Self-Flood and Self-Bail.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 0A is a graph of the relationship between lift fraction of flat plate versus its Deadrise. FIG. 0B is a graph of the relationship between pressure and deadrise angle of a wedge Upon water entry

FIG. 1A-1J depict a typical deep-V watercraft with a Concentric Pad Keel that can be attached (in FIG. 1A) or is attached (in FIGS. 1B-1J) to the bottom of the Hull of the typical deep-V watercraft.

FIGS. 2A-2C generally depict the water flow present during the impact of a Concentric Pad Keel and the water as well as the forces present during an impact of a V-Hull and the water.

FIGS. 3A-3J depict an alternate embodiment of the invention, with a Bow Pocket Vent, and Second Pad Keel that terminates at Midship.

FIGS. 4A-4B depict an alternate embodiment of the invention, with a Bow Pocket Vent and Second Pad Keel that ventilate VASFI.

FIGS. 5A-5G depict the preferred embodiment of the invention on Hull as a hull modification to a Longitudinally Stepped and Transversely Stepped Hull.

FIGS. 6A-6C depict an alternate embodiment of the invention, with a Bow Pocket Vent and Second Pad Keel that ventilate through Wedge Ventilators and Pad Keel Side Ventilators.

DETAILED DESCRIPTION

In the following description, details are presented to provide a thorough understanding: of the invention. One skilled, in the relevant art will recognize, however, that the concepts and techniques disclosed herein can be practiced without one or more of the specific details, or in combination with other components., etc. In other instances, well-known implementations or operations are not shown or described in detail to avoid obscuring, aspects of various examples disclosed herein.

“−6 to +6 Deadrise” means Deadrise of −6 Degrees to +6 Degrees and is otherwise known as “Flat” (in the case of +1/−1 Degree Deadrise). “Flat Deadrise Angles” have −6 to +6 Average Deadrise.

“6-19 Deadrise” means Deadrise greater than 6 degrees but less than 20 degrees and is known as “Low Deadrise”.

“20-45 Deadrise” means Deadrise greater than or equal to 20 degrees but less than 45 Degrees and is otherwise known as “High Deadrise”.

“>45 Deadrise” means Deadrise of 45 to 90 Degrees and is otherwise known as “Ultra High Deadrise”.

“Above” means higher in elevation when viewed from the Bow or Transom.

“Acceptable Slamming Force” is a qualitative measure of the degree of Slamming that persons on a watercraft will experience without feeling, extreme discomfort, Acceptable Slamming Force is a personal variable and is very dependent upon the rate of deceleration during a Slam.

“Angle of Attack” means the angle that the hue between fore and all points on a Hull, or a longitudinal part of a Hull, make with the incoming flow.

“Beam” is the width of a watercraft.

“Below” means lower in elevation when viewed from the Bow or Transom.

“Bow” means the forward part of a watercraft.

“Bow Pocket Vent” means an opening at the Bow on a Pad Keel Side with a Spray Deflector that provides a channel between the surface of the Pad Keel and the internal cavity of a Hollow Plenum Pad Keel.

“Chine” means the edge formed on the Hull of a flat bottomed or V-bottomed watercraft where the Hull bottom joins the Hull sides.

“Concentric Pad Keel” means a Hull structure comprised of concentric and symmetric Flat Pad Keels with the larger or Main Pad Keel Above the. smaller or Second Pad Keel. The Main Pad Keel is connected and depends below the rest of a watercraft Hull on Ultra High Deadrise Main Pad Keel Sides. The Second Pad Keel is connected and depends below the Main Pad Keel on Ultra High Deadrise Second Pad Keel Sides. There may be additional Pad Keels Above the Main Pad Keel Sides.

“Deadrise,” means (in a Transom or Bow view of the Hull) the angle of a section of a Hull relative to the water when the watercraft is not heeled over i.e. when the watercraft is upright, e.g., “Low Deadrise,” “High Deadrise,” and “Ultra High” Deadrise.

“Deep-V Hull” means a Hull with High Deadrise at the Transom when measured from the centerline of the Transom to the outboard edge of the Chine.

“Design Waterline Beam” means the width of a watercraft as measured at its waterline when loaded to its design condition.

“Design Waterline Length” means the length of a watercraft as measured at its waterline when loaded to its design condition.

“Disturbed Water Surface” means the waves or ripples caused on the water surface from a Hull entering the water.

“Fine Entry” or “Fine Entry Bow” means the shape of the Bow that is designed to slice or cleave through waves. A typical Fine Entry Bow has a Forefoot Deadrise angle greater than 45 degrees.

“Forebody” means the part of the watercraft forward of the Midship.

“Forefoot” means the part of the Keel which curves and rises to meet the Stem.

“grip” as used generically with a lowercase “g” means latitudinal pressure exerted against water by longitudinal features of a watercraft hull. Grip is useful in controlling the direction of the watercraft, particularly at high speeds. An example of usage: “Although traveling at speeds in excess of 50 knots, the watercraft's Hull had good grip and did not spin out during turns.”

“Hollow Plenum” means the internal cavity formed by the Pad Keel, Pad Keel Sides and an air and water tight top cover joining to both the Pad Keel Sides and the adjacent Hull Panel(s) Above it. It functions to conduct air or water to openings in the Pad Keel or Pad Keel Sides to Self-Bail or Self-Flood the cavity. A Bow Pocket Vent provides an access for atmospheric air entry when the Plenum is Self-Bailing or to allow air to vent out of the Plenum when the Plenum is Self-Flooding.

“hull” (in lower case letters) means the body of a prior art watercraft between the deck (which may be the inner surface of the hull) and the keel. The hull is the shaped structure of the bottom of a watercraft that provides buoyancy and seaworthiness. “Hull”, with an initial capital H, means the Hull of an embodiment of the invention described and claimed herein.

“Hull Chine Ream” means the width of a watercraft as measured between its port and starboard Chines.

“Hull Modification” means any change Or alternation made to a Hull that differs from its original design.

“Heel,” “Heeled,” or “Heeling” refer to a watercraft that is leaning either to starboard or to port.

“Immersed Area” or “Wetted Surface Area” means the wetted. portion of a Hull and appendages below the waterline.

“Initial Slam” means the initial impact of a Hull on a water surface during Re-entry, e.g. by impacting a wave or the ocean surface while a watercraft is underway.

“Keel,” means the structure of a watercraft hull that extends longitudinally along the center of its bottom and that often projects from the bottom. See also, “Pad Keel” and “Pad Keel Sides”.

“Length” is synonymous with Design Waterline Length.

“Length To Beam Ratio” is the ratio of Design Waterline Length to Design Waterline Beam. For example, a Hull with a Design Waterline Length of 30 and a Design Waterline Beam of 5 will have a Length To Beam Ratio of 6.

“Longitudinal Step” means a fore. and aft vertical discontinuity on the Hull bottom surface and appears as a step when viewed in Transom or Bow views.

“Main Pad Keel” or “MPK” means the Pad Keel in a Concentric Pad Keel configuration Above the Second Pad Keel.

“Main Pad Keel Sides” means the Ultra High Deadrise Hull Panels that connect the Main Pad Keel and depend from the remainder of the Hull Above it.

“Midship” means the location on a watercraft that k approximately equally distant from Bow and stern, e.g. a location between 40% and 60% of the length from Bow to stern.

“Pad Keel” means the flat pad Hull surface that projects below the theoretical convergence of the sides of the watercraft's V-shaped Hull. Pad Keels increase hydrodynamic lift compared to traditional keels when a watercraft is underway.

“Pad Keel Sides” means the Ultra High Deadrise Hull Panels that connect as Pad Keel and depend from the remainder of the Hull Above it.

“Pad Keel Side Ventilator” means a Pad Keel Side Hull Panel that is inwardly-stepped towards the centerline from the Pad Keel Sides, tapers at its aft end to blend with the Pad Keel Sides, and has one or more openings at its forward end, through which air and water can Self-Bail and Self-Flood the Hollow Plenum and provide air ventilation to the Panels aft of it when the craft is underway.

“Panel” means a plating component of a Hull. A combination of Panels and other components of a Hull form the Hull itself.

“Planing” means riding on the surface of water as in “hydroplaning” or “aquaplaning,” where lift is provided by hydrodynamic pressure.

“Planing Hull” means a Hull shape that allows at least part of its Keel to rise above the water's free surface, and to ride up on the after part of the Hull, allowing the watercraft to move much faster with some of the watercraft on the surface of the water.

“Planing Surface” or “Planing Surfaces” mean a section, or sections, of a Hull having Flat Deadrise Angles that operate to ride at least partially on the surface of water when a watercraft is underway.

“Plenum” is a synonym of “Plenum”.

“Re-entry” means the reentry of a watercraft hull into a water surface after all or part of the hull has left the water's surface, typically when the watercraft is underway, e.g., through choppy water or has been launched off a wave crest.

“Rough”, “Rough Water”, or “Rough Seas” are synonyms that man wind and wave conditions that cause uncomfortable watercraft motions.

“Seakeeping” or “Seakeeping ability” are synonyms for the qualitative measure of a watercraft's ability to maintain functionality in Rough Water.

“Seakindly” or “Seakindliness” are synonyms for the qualitative measure of a watercraft's ability to maintain occupant comfort in Rough Water.

“Second Pad Keel” or “SPK” means the Pad Keel Below the Main Pad Keel on a Hull narrower than the Main Pad Keel.

“Second Pad Keel Sides” means the Ultra High Deadrise Hull Panels that connect the Second Pad Keel and depend from the Main Pad Keel.

“Self-Bailing” or “Self-Bail” means a feature of a watercraft that drains water by air pressure or gravity, e.g. through an opening or by pressure gradient.

“Sell-flooding” or “Self-flood” means a feature of a watercraft that allows water to enter and flood an internal Plenum automatically, e.g. by water pressure alone.

“Slam” or “Slamming” means to crash down hard on a water surface, referring to the action of a watercraft.

“Spray Deflector” means a covering on a Bow Pocket Vent that prevents incoming spray from entering the opening.

“Stem” means the forward most part a the Bow.

“Taper” means a decrease in width in the aft to fore direction of a watercraft

“Transom” means the flat surface forming the stern of a watercraft.

“Transverse Step” means a port to starboard (athwartship) vertical discontinuity to a watercraft's Hull and it appears as a step in the Hull bottom in a side view,

“Transversely Stepped” means a Hull including a single or multiple Transverse Steps.

“Ultra High Deadrise” or “UHD” refers to a Hull, or portion of a Hull, that is sharply V-shaped and has a Deadrise angle of between 45 and 90 degrees.

“Undisturbed Water Surface” means the surface of water yet to be entered by the Hull.

“VASFI” or “Ventilated Aft Swept Flow Interrupter” has the meaning as defined and used in U.S. Pat. No. 7,845,301, entitled “Ventilated Aft Swept Flow Interrupter”, to Loui et al.

“Ventilate” means to conduct atmospheric air outboard through submerged Hull openings to partially un-wet submerged Hull surfaces using a negative pressure gradient caused by the Venturi effect while the craft is underway, The un-wetting of submerged Hull surfaces reduces the Hull's Viscous Drag.

“Ventilating Air” means atmospheric air used to Ventilate the Hull.

“V-Hull” means a Hull composed of two distinct planar surfaces that intersect at the Keel at a Deadrise angle. A V-Hull is so-named because it resembles the shape of the letter “V” in Bow view.

“Viscous Drag” is friction force acting opposite to the relative motion of a watercraft moving through a fluid.

“Water Entry Deceleration” means, with reference to a Hull entering water, or a portion of a Hull entering water, the deceleration of a Hull as the Hull enters the water.

“Watercraft Re-Entry Initial Deceleration” means, with reference to a Hull Re-entering water, or a portion of a Hull Re-entering water, the deceleration of a Hull as the Second Pad Keel Re-enters the water.

“Watercraft Re-Entry Vertical Deceleration” means with reference to a Hull Re-entering water, or a portion of a Hull Re-entering water, the decrease in vertical velocity of the Hull as the Hull Re-enters the water.

“Waterline” means the level normally reached by the water on the side of a watercraft.

“Wedge Ventilator” means a wedge shaped Hull Panel that projects downward at its aft end from a Longitudinal Step, tapers at its forward end to blend with the Longitudinal Step, and has one or more openings at its aft end, through which air and water can Self-Bail and Self-Flood the Hollow Plenum and provide air ventilation to the Panels at of it when the craft is underway.

A watercraft's Planing performance efficiency is improved and a reduction in Slamming Forces is realized by having a Concentric Pad Keel structure configuration. A watercraft designed with a Concentric Pad Keel in accordance with the teachings provided herein has a Flat Main Pad Keel projecting downward on Main Pad Keel Sides from a typically V-shaped watercraft Hull. The Main Pad Keel has Main Pad Keel Sides with Deadrise angles between 45 degrees to 90 degrees. The height of the Main Pad Keel sides at the Transom is 20% to 30% of the Main Pad Keel width at the Transom. The Main Pad Keel is widest at the Transom and its width Tapers towards the Bow. A Second Pad Keel, smaller than the Main Pad Keel, projects downwards from the MPK on Second Pad Keel Sides with Deadrise angles between 45 and 90 degrees. The Second Pad Keel is narrower and on the same longitudinal centerline as the Main Pad Keel and extends the full or optionally only a partial length of the Main Pad Keel. The average width of the Main Pad Keel, and Second Pad Keel at the Transom for a watercraft with a Length to Beam Ratio of less than four (4) is 15% to 25% of the Hull's Chine Beam measured at its Transom. The average width of the Main Pad Keel and Second Pad Keel at the Transom for a watercraft with a Length To Beam Ratio of four (4) or greater is 20% to 30% of the Hulls Chine Beam measured at its Transom.

Shown in FIG. 1A is a Transom view 100 of a typical Deep-V watercraft with an exploded view of a Concentric Pad Keel 102 that is detached from the Hull 104 in FIG. 1A and is shown attached to the bottom of the Hull 106 in FIGS. 1B to 1J. FIG. 1B is a bottom view 108 of this watercraft and FIG. 1C is a side view 110 of this watercraft. FIGS. 1D through 1H are section views of this watercraft from the Forefoot 112 to the Transom 114 whereby the Main Pad Keel 116 projects downward from the bottom of the Hull 104 on Main Pad Keel Sides 118 of 49 degrees. A Second Pad Keel 120 projects downward from the Main Pad Keel 116 from Second Pad Keel Sides 122 of 90 degrees. FIG. 1J shows an isometric (aka perspective) view 124 of this watercraft. The Main Pad Keel 126 and Second Pad Keel 128 extend longitudinally from their apex at the Bow 130 all the way to the Transom 132. The Main Pad Keel 126 and Second Pad Keel 128 are widest at the Transom 132 and Taper in width towards the Bow 130. The watercraft has as Design Waterline Length of 18.4′ and a Design Waterline Beam of 7′. Its Length to Beam Ratio is 2.62 and the average width of the Main Pad Keel 126 and Second Pad Keel 128 at the Transom 132 is approximately 15% of its Hull Chine Beam 134 at the Transom 132.

When the Hull 106 of the watercraft shown in FIGS. 1A to 1J reenters the water after becoming partially or fully airborne from the water's surface, the Second Pad Keel 128 is the first Hull structure to make contact. The dimensions of the Second Pad Keel 128 are selected. such that its impact generates an Acceptable Slamming Force when falling. The Second Pad Keel 128 impact imparts downward momentum to the water with a force perpendicular to its surface. FIG. 2A shows the flow directions 202 of the displaced water 204 resulting from a Pad Keel 206 entering the water surface with vertical velocity “v” 208. The watercraft experiences Watercraft Re-Entry Initial Deceleration from the large vertical momentum imparted by the Second Pad Keel 206 to the water 210 under it. Compare this to the water displacement 212 in FIG. 2B as the result of a V-shaped structure 214 entering the water surface 216 with vertical velocity “v” 218. The impact forces act normal to its immersed Hull panels 220 resulting in lower vertical momentum imparted to the water 222 as a result of its Deadrise angle 224 and therefore lower Watercraft Re-Entry Vertical Deceleration compared to the Flat Pad Keel 206.

The Main Pad Keel 226 impacts the water surface 228 shortly after the Second Pad Keel 230 and at a lower velocity than the Second Pad Keel 230 impact as a result of the Watercraft Re-Entry Initial Deceleration. This Main Pad Keel 226 impacts a Disturbed Water Surface 232 that has been displaced circumferentially by the impact of the Second Pad Keel 230. Also, the water 234 below the Main Pad Keel 226 and immediately adjacent to the Second Pad Keel Sides 236 is accelerating downwardly as shown by the flow direction 238 in FIG. 2C. The result of these factors is to reduce the force of a Slam of the Main Pad Keel 226 compared to if it had landed on an Undisturbed Water Surface without a Second Pad Keel 230 landing immediately before it The Concentric Pad Keel arrangement 240 therefore allows a watercraft having a wider Main Pad Keel 226 to have a Slam force that is comparable to a narrower Pad Keel 206 without a Concentric Pad Keel arrangement 240.

As the watercraft continues its downward Re-Entry, it experiences additional high Water Entry Deceleration from the large vertical momentum imparted to the water under the wider and larger Immersed Area of the Main Pad Keel 226. Next, the Main Pad Keel Sides 242 become immersed. It is well known that Hull Panels with UHD angles when Re-Entering the water surface 228 have relatively small changes in pressure measured normal to the immersed Hull Panel surfaces. As the immersion of the Main Pad Keel Sides 242 progresses, it does not contribute a significant amount to further Water Entry Deceleration, however, the large vertical momentum imparted to the water under the Main Pad Keel 226 and. Second Pad Keel 230 continues.

When the Concentric Pad Keel 240 is folk; immersed, the ongoing Water Entry Deceleration from the Concentric Pad Keel 240 has continued long enough that the watercraft vertical plunging velocity 244 has slowed. Therefore, when parts of the Hull above the Main Pad Keel Sides 242 impact the water surface, the Slamming forces are Acceptable Slamming Forces.

FIGS. 3A to 3J show another embodiment of the invention. The Second Pad Keel 302 of the Concentric Pad Keel 304 terminates at Midship 306, rather than extending longitudinally the full length of the watercraft to the Transom 308.

FIG. 3A shows the Bow Pocket Vents 310 located on the forward end of the port and starboard Main Pad Keel Sides 312, adjacent to and aft of the Bow Stem 314. This opening, has a Spray Deflector 316 “pocket” to allow atmospheric air to vent the Hollow Plenum 318. On the forward bottom of the Main Pad Keel 320 is an opening 322 to allow air to vent the Second Pad Keel Plenum 324, The aft end of the Second Pad Keel Plenum 324 is open, allowing air to ventilate the Hull surfaces aft of the outlet to reduce Wetted Surface Area and. Viscous Drag at Planing speeds.

At zero and low speeds the Concentric Pad Keel Plenums 318, 324 Self-Flood with water entering, through the Plenum openings 322 below the water surface and displace air in the Plenum which exits through the Bow Pocket Vent 310. Water in the Plenums lowers the vertical center of gravity of the watercraft to reduce motions at zero- and low speeds, to improve Seakeeping, and to improve Seakindliness. When the watercraft accelerates to Planing speeds, the Bow Pocket Vent 310 rises above the water surface, and the intake air feeds into the Plenums 318, 324 of the Concentric Pad Keel, which Self-Bail through outlets 322 on the Concentric Pad Keel.

Cross-sections 326 of the Concentric Pad Keel 304, given in FIGS. 3D through 311, show the Main Pad Keel Plenum 318 and the Second Pad Keel Plenum 324 terminating near mid-length 306 of the Main Pad Keel 320 and at the aft end of the Second Pad Keel 302.

FIG. 3J shows an exploded bottom isometric view 328 of the Concentric Pad Keel 304, and shows the Self-Flood and Self-Bail channel openings 330 between the Main Pad Keel Plenum 318 and the Second Pad Keel Plenum 324.

In another embodiment of the invention, the air in the Hollow Plenums of the Concentric Pad Keel 402 is used to provide ventilating air to VASFI 404 such as those shown in FIG. 4A and 413. In this embodiment, the Main Pad Keel Plenum 406 is filled with air through a Bow Pocket Vent 408 at Planing speeds, then ventilates to openings 4.10 aft of each VASFI 404 and to a Second Pad Keel Plenum 412. The Second Pad Keel Plenum 412 then ventilates surfaces all of the outlet 414 at the aft end of the Second Pad Keel Plenum 412.

FIGS. 5A to FIG. 5G show the preferred embodiment of the invention, this is a Hull Modification of a Longitudinally Stepped and Transversely Stepped Hull disclosed in U.S. Pat. No. 8,210,116. In this configuration, the Concentric Pad Keel is different in three portions of the Hull.

Forward of station 3 in FIG. 5B, the Second Pad Keel Sides 502 have a constant Deadrise angle of 50 degrees (FIG. 5F) and the Second Pad Keel 504 width Tapers until it completely blends into an apex 506 at the Hull's Forefoot, forward of station 80 (FIG. 5G). The Main Pad Keel 508 has a 0.5 degree Angle Of Attack relative to the bottom plane of the Second Pad Keel 504 and the Main Pad Keel 508 width also tapers toward the Bow 510. The Main Pad Keel Sides 512 have a constant Deadrise angle of 90 degrees in this portion of the Hull.

In the middle portion, between station 3 and station 1 in FIG. 5B, the Second Pad Keel Sides 514 and Main Pad Keel Sides 516 both have a constant Deadrise of 90 degrees.

In the aft portion, between station 1 and station 0 in FIG. 5B, there is no Second Pad Keel and the Main Pad Keel Sides 518 have a constant Deadrise of 90 degrees.

In another embodiment of the invention, air in the Hollow Plenums 602 of the Concentric Pad Keel 603 is used to provide ventilating, air to Hull Panels through Wedge Ventilators 604, Pad Keel Transverse Steps 606, and Pad Ked Side Ventilators 608. In this embodiment, air enters the Plenum through a Bow Pocket Vent 610 and exits through openings 612 in the Pad Keel Transverse Step 606 at the aft end of each Wedge Ventilator 694, and the forward end of each Pad Keel Side Ventilator 608. Air exiting, these openings 612 then ventilates the Longitudinal Step 614, Main Pad Keel 616, and Main Pad Keel Sides 618. FIG. 6A is an exploded bottom isometric view 620 of the Concentric Pad Keel 603 that is detached from the Hull 622 in FIG. 6A, and shows a close-up view of the Bow Pocket Vent 610, where the opening is protected by a Spray Deflector 624. The Concentric Pad Keel 603 is shown attached to the bottom of the Hull 622 in FIGS. 6B and 6C.

Included, but not shown in FIGS. 5A-G, the preferred embodiment, is a Bow Pocket Vent and Plenums. The omission of a Bow Pocket Vent and or one or more Plenums in the description of other embodiments does not preclude their inclusion in the other embodiments.

It will be appreciated to those skilled in the art that the preceding examples and embodiments are exemplary and not limiting to the scope of the present invention. It is intended that all permutations, enhancements, equivalents, and improvements thereto that are apparent to those skilled in the art upon a reading of the specification and a study of the drawings are included within the true spirit and scope of the present invention. It is therefore intended that the following appended claims include all such modifications, permutations and equivalents as fall within the true spirit and scope of the present invention. 

What is claimed is:
 1. A watercraft including a Deep-V Planing Hull comprising: a Fine Entry Bow; a Transom; and a Concentric Pad Keel having, a Main Pad Keel projecting downward from the Deep-V Planing Hull on Ultra High Deadrise Main Pad Keel Sides, and a Second Pad Keel projecting downward from the Main Pad Keel on Ultra High Deadrise Second Pad Keel Sides that Tapers from the Transom to an apex at the Forefoot of the Fine Entry Bow.
 2. The watercraft of claim 1, wherein the watercraft has a Waterline Length To Beam Ratio of less than 4 and the Main Pad Keel and Second Pad Keel have an average width between 15 percent to 25 percent of a Hull Chine Beam at the Transom.
 3. The watercraft of claim 1, wherein the watercraft has a Waterline Length To Beam Ratio of 4 or greater and the Main Pad Keel and Second Pad Keel have an average width between 20 percent to 30 percent of a Hull Chine Beam at the Transom.
 4. The watercraft of claim 1, wherein the Main Pad Keel Sides have Deadrise angles between 45 degrees to 90 degrees: and wherein the Main Pad Keel Sides have a height that is between 20% to 30% of a width of the Main Pad Keel.
 5. The watercraft of claim 1, wherein the Deep-V Planing Hull is Longitudinally Stepped and Transversely Stepped; and wherein the Ultra High Deadrise Second Pad Keel Sides have a constant angle of 50 degrees forward of a station 3 of the Deep-V Planing Hull and a constant angle of 90 degrees between station 3 and a station 1 of the Deep-V Planing Hull; and wherein the Ultra High Deadrise Main Pad Keel Sides have a constant Deadrise angle of 90 degrees.
 6. A watercraft including a Planing Hull comprising: a Fine Entry Bow; a Transom; a Concentric Pad Keel including, a Main Pad Keel constructed with a Hollow Plenum, the Main Pad Keel having one or more Bow Pocket Vents allowing air to vent a Hollow Plenum, and a Second Pad Keel having an opening at an aft end of the Second Pad Keel allowing Ventilating Air to Ventilate the Main Pad Keel.
 7. The watercraft of claim 6, wherein Planing Hull includes a VASFI and the Hollow Plenum provides Ventilating Air to the VASFI.
 8. The watercraft of claim 6, wherein the Planing Hull includes one or more transverse steps to the Main Pad Keel and Second Pad Keel and the Hollow Plenum provides Ventilating Air to the Transverse Steps.
 9. The watercraft of claims 6, wherein the Planing Hull includes a Pad Keel Side Ventilator, and the Hollow Plenum provides Ventilating Air to the Pad Keel Side Ventilator.
 10. The watercraft of claims 6, wherein the Planing Hull includes a Wedge Ventilator and the Hollow Plenum provides Ventilating Air to the Wedge Ventilator.
 11. A Concentric Pad Keel operable to reduce Slamming, comprising: a Main Pad Keel extending downward from Ultra High Deadrise Main Pad Keel Sides; wherein the Ultra High Deadrise Main Pad Keel Sides have Deadrise angles between 45 degrees to 90 degrees; wherein the height of the Main Pad Keel Sides at a Transom are between 20% to 30% of a Main Pad Keel width; a Second Pad Keel projecting downward from the Main Pad Keel on Ultra High Deadrise Second Pad Keel Sides with deadrise angles between 45 and 90 degrees; wherein the Second Pad Keel is narrower than the Main Pad Keel; wherein, in operation, a watercraft incorporating the Concentric Pad Keel becomes partially or fully airborne from a water surface; wherein the watercraft reenters the water surface after falling; wherein the Second Pad Keel is a first Hull structure of the watercraft to make contact with the water surface upon reentering the water surface; wherein the impact of the Second Pad Keel on the water surface generates an Acceptable Slamming Force; and wherein the Main Pad Keel is a second Hull structure of the watercraft to make contact with the water surface as the watercraft reenters the water surface. 